This patch adds DP-MST support for GK104+ NVIDIA codecs.

GK104+ NVIDIA codecs support DP-MST audio. These codecs have 4
output converters and 4 pin widgets, with 4 device entries per pin
widget for a total of 16 device entries.

This patch moves the existing patch_nvhdmi() definition to
patch_nvhdmi_legacy(), used by pre-GK104 NVIDIA codecs. Redefine
patch_nvhdmi() to enable DP-MST support by setting codec->dp_mst and
spec->dyn_pcm_assign.

Introduce fresh logic for dynamic pcm assignment, making
sure that new pcm assignments are compatible with the legacy static
per_pin-pmc assignment that existed in the days before DP-MST.
Signed-off-by: Nikhil Mahale <nmahale@nvidia.com>
Reviewed-by: Aaron Plattner <aplattner@nvidia.com>
Link: https://lore.kernel.org/r/20191119084710.29267-5-nmahale@nvidia.comSigned-off-by: Takashi Iwai <tiwai@suse.de>